Thread cutter



June 24, 1930. H. LINDNER THREAD CUTTER Filed April 8, 1924 mil? Patented June 24,1930 i 1,768,089,

UNITED STATES PATENT OFFICE HERBERT LINDNER, OF BERLIN, GERMANY THREAD CUTTER Application filed April 8, 1924, Serial No. 705,060, and in Germany April 25, 1923.

-This invention relates to improvements Figure 6 is a diagram showing the mode in screw thread cutting taps of that class of operation of the tap. in which the body of thetap is tapered The tap 1 is provided in the usual manner toward its free end and is provided with with grooves a between which are the racks a plurality of longitudinal grooves between or rows of teeth. In Figure 1 two rows 2 55 which grooves are the racks of segmental and 4 are shown.- The teeth of several cutting teeth. racks are formed in helical arrangement. The object of the invention is to effect The circumferential surfaces of the teeth improvements in the construction of the are narrowed so that the width of the cirteeth so as to greatly improve the capacity cumferential cutting edge, normally pro- 60 and thread cutting efiiciency of'the tap by duced by the conical form of the first out, substantially equalizing the cutting work of portion is distributed in the operation of the teeth and reducing the cutting work of the tap on several successive teeth of the suceach tooth so that the teeth succeed one cessive racks. In other words the circumanother and each cuts only a portion .of the ferential surfaces 0 located between the 65 thread, flanks (l are reduced in length, axially of A specific object of the invention is to he tap. That is to say, the peripheral porprovide each t th, th fla k r sid f tion of each tooth is provided with a reduced which located at the grooves of the body ap d I rebated peripheral portion 6 0 present and form the cutting edges proper, which is es de e p ip ral por ion 6- 70 with projections which are of less width S HCtiOH hanges around the tap in than the peripheral portion of the tooth and h manner that the one tooth of one rack which projections of the series of teeth folis r duced at its upper flank, the following lowing each other around the tap are artooth of the next successive rack is reduced ranged in taggered relation so that their at Its lOWQI flank, the tOOtll Of the next cutting edges or flanks are located on difl'er- Successive k at i pper fl nk and-S0 0n ent portionsof the rows of teeth distributed from tooth to tooth p y around the y spirally around the t body of the tap from the tapered end to where \Vith the above and other objects in view, e reduction f h leng h of the Cutting the invention consists in the construction edges finally Ceasesc and arrangement of parts hereinafter 'de- The reduction of the axial length of the scribed and clai d, I I cutting edges is not uniform along the tap, In th accompanying d i but decreases from the tapered end to the Figure 1 is a diagr ti xi l ti other end thereof and ceases at a point somethrough about one half of a tap constructed What IBIIIO'EB f the o h r nd Wh re it in ac ordan with thi i ti becomes zero. This appears distinctly from Figure 2 is a diagrammatic section on a Flgure whichiare Shown two rows of larger scale through the rack of teeth on. teeth; W11? 51 left hand TOW the teeth the left hand sideoof the tap, Figure 1, of Whlch have .upperv flanks '3 and lower with additional lines to facilitate the disflanks d fight hand row or a 4 the teeth of which have lower flanks 5 and upclosure of the invention. a

Figure 3 constitutes a series, in four parts, g g g g fi 2' 2%: g i f lf 525 3232 53 of sections illustrating a modification of the in the teeth 4 the lower flanks 5 those mve ntlon' which are reduced in axiallength. The Flgllre 15 a detall Sectlonal Perspectlve said figure shows distinctly thatthe lengt Showmg one the t e racks h of the cut off portions of the cutting edg s tap on an enlarge l become shorter and shorter upwardlynor t Figure 5 isa transverse sectional view' ward the inner end. of the tap, until the 50 of the tap. I zero point is reached, and that reduction takes place only from the tapered portion of the tap.

In apportioning thenormal breadth of resultingfrom the displacement of the upper orlower or of both to the flanks 3 and 5, would, however, be' only one-third of the normal breadth. It is immaterial whether 'tion 0 by the displacement of the flanks 3 and 5 that' there be formed on the shaft of the tap a cylindrical surface 10, as such surface does not come in contact with the work piece to be provided with a thread in the tap.

The modification shown in Figure 2 is a diagrammatic section of one rack of teeth, the plane of which section is in the teeth 4 and the consecutive teeth 2 which are located in staggered relation to the teeth 4 appear in perspective. The thread to be cut by the teeth is indicated in"'dotted lines. 8 denotes the-uppersides of the teeth 4 and 5 denotes the lower sides .or flanks of the operating portions 0 of the teeth and every tooth doing cutting work is cutting at the same width as the preceding tooth and also deeper than the preceding tooth, as such cutting edges come into action successivel because of their arrangement in staggere relation to one another, as well as to the. bearing teeth.

It will be understood that in accordance I with this invention stocks and so-called screw dies for stocks and dies for thread cutting machines may be also constructed and that a thread cutting device thus formed may be operated at higher speed and with greater facility than heretofore.

Having thus described my invention, I claim:

A screw tap, comprisinga body tapered such teeth. 3 denotes the upper flanks of:

the teeth 2 and 6 denotes the lower flanks thereof. 7 indicates the cutting edges of the teeth 4 and 9 indicates the cutting edges of the teeth 2. The alternation as it appears in Figure 2 is continued around a tap in spirals. Each cutting edge is reduced in length, that is to say, axially of the tap, as in the form shown in Figure 1. An important feature of construction is that the reductions of the cutting edges alternate from tooth to tooth along the entire length of the helical line formed by the consecutive teeth and the. axial length of the remaining portions of said teeth diminishes from the tapered end to the body of the tap as shown. a

In case the breadth of the peripheral cutting. surface is one half that of the periphery, as is shown in the example-5'15, Figure 3, then at every second tooth the lower part of its cutting edge is setback at the circumference, so that each such tooth is made shallower by the set back portion of its periphery.

The teeth following each other in first cutting, that is to say on the tapered por-.

tion of the tap, are designated 2-25 and the peripheral cutting edges may in such teeth be either on the line k /s or more or less behind or within such line to provide for all the teeth and approximately equal cutting sectional area. The shape of the usual rst cut is paraboloid.

It is preferable that the curve produced.

by the greater or less recession of the cutting edges behind the line lc k will, toward the end of the first cutting portion of the tap,

run out rather abruptly into the cylinder formed by the main portion thereof. By such construction the stress on the inthe direction toits free end and having. a plurality or longitudinal grooves, ledgelike racks located between said grooves and constitutingthe remainder of the body, teeth on said racks having peripheral projections, the flanks of said teeth'being located at the said grooves and presenting the cutting edges proper, said peripheral projections of theteeth of the respective racks following each other around the tap in staggered arrangement so that their cutting flanks are located on different portions of the racks of teeth distributed around the tap body.

2. A screw tap, comprising a body tapered in the direction to its free end and having a. plurality of longitudinal grooves, ledgelike racks located between said grooves and I constituting the remainder of the body,

teeth on said racks having peripheral proout frictionthrough the cut made by the preceding projection.

In testimony whereof I aflix my signature. v v

HERBERT LINDNER. 

